It is known to enhance the mechanical properties of the manufactured articles based on polymeric plastic material by incorporating therein reinforcing fibrous materials endowed with a high elastic flexural modulus, such as fibers of glass, of cellulose, of asbestos, of carbon, etc.
Methods employed for preparing articles so reinforced are those based on pressure-injection of mixtures of molten polymer and fibers, which however are suitable for preparing small-size articles and involve non-homogeneity of the article reinforcement in its area of greatest bending; or are the methods consisting in the impregnation of fiber layers with polymeric latexes followed by hot molding of the resulting panels. In the latter case, the fibrous material is predominantly located in the central area of the article and does not contribute to the reinforcement.
Furthermore, a defect common to both methods is that the surface of the article has an esthetically flawed finish, due to the fact that the fibrous material appears on the surface, which flaw is favored by the molding operation.